Semi-mechanical telephone system.



A. M. BULLARD.

SEMI-MECHANICAL TELEPHONE SYSTEM,

APPLlCATION FILED APR.3, 1907.

Patented Feb. 2, 1915.

11 SHEETSSHEET 1.

[72 U672 [02 K bev'f J/Z Ballard J: m m WEN n \SN WU .99 M. US. WW k Q w m ES @Q A. M. BULLARD.

SEMI-MECHANICAL TELEPHONE SYSTEM. APPLICATION FILED APR. 3, 1907.

1,126,952. Patented Feb. 2, 1915.

11 SHEETS-SHEET 2.

A. M. BULLARD.

SEMI-MECHANICAL TELEPHONE SYSTEM.

APPLICATION FILED APR. 3, 1907 1,126,952. Patented Feb. 2, 1915.

11 SHEETS-SHEBT 3.

Q\ N a;

2 21 27? my Se lee/Tor [nvenlar 5 v fi/berl f. ELM/an! A. M. BULLARD.

SEMI-MECHANICAL TELEPHONE SYSTEM.

11 SHEETSSHEET 4.

(S Umm b NNm A. M; BULLARD. SEMI-MECHANICAL TELEPHONE SYSTEM.

APPLICATION IILBD APR. 3, 1907.

Patented Feb. 2, 1915.

11 SHBETPSHEET 5.

A. M. BULLARD.

SEMI-MECHANICAL TELEPHONE SYSTEM. APPLICATION FILED APR.3,1907.

1,126,952. Patented Feb. 2, 1915.

11 SHEETSSHEET 6.

A. M. BULLARD. SEMI-MECHANICAL TELEPHONE SYSTEM. APPLICATION FILED APR. 3, 1907.

1 ,126,952, Patented Feb.2, 1915.

11 SHEETSSHEET 'l.

a \J E +5, 5 b I L H- e .b .8 g a 3 P\ Q: a R

O; ON

w frwenfor Lnesses. m m

L I N filerl mfjullard M315 L: y flww A. M. BULLARD.

SEMI-MECHANICAL TELEPHONE SYSTEM.

APPLICATION FILED APR. 3, 1907.

Patented Feb. 2, 1915.

11 SHEETS-SHEET 9.

WNN,

mwwm

bmww

lllIlHill i Q I HI A. M. BULLARD. SEMI-MECHANICAL TELEPHONE SYSTEM.

APPLICATION TILED APR. 3, 1907.

Patented Feb. 2, 1915.

Vii g ge ii /6! f/Zba [lard A. M. BULLARD. SEMI-MECHANICAL TELEPHONE SYSTEM.-

APPLICATION FILED APR. 3, 1907.

11 SHEETS-SHEET 11.

M 5 5 2/5: 12?. Ballard MAMA yfi UNITED STATES PATENT OFFICE.

ALBERT M. BULLARD, OF NEW YORK, N. Y., ASSIGNOR T0 WESTERN ELECTRIC COMPANY, OF CHICAGO, ILLINOIS,

A CORPORATION OF ILLINOIS.

SEMI-MECHANICAL TELEPHONE SYSTEM.

To all whom it may concern Be it known that I, ALBERT M. BULLARD, citizen of the United States, residing at New York, in the county of New York and State of New York, have invented a certain new and useful Improvement in Semi-Mechanical Telephone Systems, of which the following is a full, clear, concise, and exact description.

My invention relates to a telephone exchange system of, for example, the semimechanical type, wherein the operator answers the call of a subscriber in the usual way by uniting her connecting circuit with the line of such subscriber, and mechanical switching mechanism completes the connection by uniting the operators connecting circuit with the called line, the operation of the switching mechanism being controlled by sending apparatus adapted to be actuated by the operator to selectively operate said switching mechanism.

In a telephone exchange system embodying my invention, connectors are provided at the central ofiice adapted to complete connection with different groups of lines. ,A distributer or primary selector is provided, adapted to unite a given talking circuit or operators connecting circuit with a connector serving a given group of lines, orwith an idle connector in a set of connectors serving the same group. I

The grouping of telephone lines at the connectors and of trunking lines leading to the connectors may be on a non-decimal basis, the total number of telephone lines at each connector being evenly divisible into the decimal number 1000, said quotient being a multiple of 10, thereby permitting a decimal arrangement of digit keys representing the digits of subscribers line numbers, so that when keys representing a particular line are depressed, they operate without intervention of translating devices, line switching mechanism being adapted to select the group of lines containing the called line, and to connect with the desired line in such group. For example, lines may be arranged in groups of 500, and keys representing the thousands, hundreds, tens and units digits of subscribers lines selectively operate the line switching mechanism.

The operators connecting circuit is adapted to be connected witha distributer or primary selector in either the local or a distant Specification of Letters Patent.

Application filed April 8, 1907.

Patented Feb. 2, 1915, Serial No. 366,197.

oflice, said selector beingarranged to connect with an idle connector adapted to reach the line of the called party. Each connector may be arranged to reach, for example, five hundred lines. The operator is provided with a sending apparatus having, for example, thousands, hundreds, tens and units digit keys, which control the operation of the primary selector and a connector selected thereby to complete the connection of the pperators connecting circuit with a desired Heretofore, it has been customary always to provide the connectors with'relays for testing and ringing the called lines. In an exchange where the total number of connectors exceeds the total number of distributers or primary selectors there is obviously economy in transferring said relays to the latter, and one feature of my invention consists in providing for this transfer, so that? the relays act upon any line chosen by the connector selected by the primary selector.

When a connector is selected by the dis tributer or primary selector, a normaily open test conductor extends from the test brush of the connector arm back through the distributer, where the establishment of its continuity is controlled. Said test conduct'or is completed when the connector unites with the desired line, and may include at the distributer mechanism adapted, in case the line of the'called party is busy, to apply a busy signal to the talking circuit of the distributer; and also may effect the' automatic restoration of'the distributer and connector to normal condition. The said testingconductor is preferably normally open at two points, at the connector and at the distributer, and preferably extends from the test brush of the connector over the local wire thereof, through normally-open contacts' to one of the line conductors leading back to the primary selector, and at said selector a local conductor may lead from the line wire through normally open contacts to one pole of a source of current, the other pole whereof is connected with the local line terminals upon the connector. A pair of continuity relays may be provided for closing said two sets of normally open contacts-and a relay at the selector is arranged to be operated when the connector has united with the desired line to operate said pair of relays and close the test conductor. c

Within the test conductor may be included relays at the connector and the primary selector, said relays being arranged to be unresponsive in case the called line is busy, preferably by means of a shunt existing around said conductor, due to the busy condition of the called line, the relay at the connector responding in case the called line is free to disconnect the local wire of the connector and the circuits of its operating mechanism from the line conductors. The

relay at the primary selector is adapted, in 1 case the called line is busy to effect the con-" nection of the busy signal apparatus with the talking circuit or operators connecting circuit. If, however, the called line is free, said relay when operated disconnects the local conductor at the primary selector, which forms a part of the testing conductor, from the line circuit, and may also serve to establish the continuity of the talking conductors. may in attracting their armatures include themselves in locking circuits under the control of the retaining magnets of the connector and primary selector.

Another feature of the invention relates to the provision of automatic signaling apparatus at'the primary selector, which is brought into service when connection is completed by the connector with a free line, to signal the called party. I preferably employ tl-J connecting relay at the distributer to operate when energized a ringing relay which severs the line conductors v and connects the portions thereof leading through the distributer and connector to the called line, with the poles of the ringing generator. A relay may also be provided in the ringing circuit which responds when the called party answers and effects the deenergization of the ringing relay. The circuit of the ringin relay as eom pleted by the connecting re trolled in normally closed co'ntacts of the continuity relay of the primary selector, and the relay in the ringing circuit before referred to may when energized complete a circuit for said continuity relay, to cause the same to open the circuit of the ringing relay and lock itself'up under the control of the retaining magnet of the primary selector. I

I also provide at the primary selector means for automatically signaling a called station of a party line. The testing circuit 1 may include a relay at the selector adapted to control the character of current, for example, negative and positive, to be applied through the selector and connector, to the called line. Said relay may be arranged to be unresponsive to the current in the testing circuit in case the called station is a member of a party line that requires signaling current of a given polarity, for example,

Said connecting relays ay may be 0on negative, and said relay may respond in case the called station is a member of a party line and requires signaling current of an opposite polarity, for example, positive. I preferably employ a relay for this purpose having two windings, one of said windings being included in the testing circuit and the other of said windings, which I will term the holding winding, being short circuited at the armature and back contact of said relay. Therefore, when the relay is initially energized, its armature is attracted and in its movement opens the short circuit about the holding winding of said relay, whereupon said winding is included in a locking circuit with the connecting relay; said circuit, in case the relay had not been initially energized, would include only the armature and back contact of said relay. The said relay may control the application of the current of different charactor to the contacts operated by the ringing relay above referred to.

Where private branch exchanges are associated with a system, such as I have referred to, connectors serving a given group of lines may include a set of terminals representing a group of trunk lines leading from the main exchange to the private branch exchange. The operation of line selection by the primary selector and connector, as governed by the controlling mechanism or sending apparatus associated with the connecting circuit, would simply advance the connector brushes to terminals of the first trunk line. Now, if this trunk line is busy, it is necessary to advance the brushes to the next trunk line terminals and so on until an idle trunk line is reached, and this must be done, of course, independently of the original controlling mechanism or sending apparatus. 1 have provided, therefore, at the primary sclector, mechanism which is brought into service when the connector brushes reach the terminals of a busy trunk line leading to a private exchange, to advance the connector brushes to the next trunk line terminals. The test terminals of all the trunk lines but the last, leading to a given branch exchange, may be supplied with current of a polarity opposite to the polarity of the current supplied to the test terminals of the subscribers lines terminating at the same connector, and a. polarized relay may be provided at the selector in the testing circuit, responsive to the polarity of current present at the said trunk line terminals, except the last. Thus, in case the first trunk line tested were in use, the polarized relay referred to would operate while the connecting relay would be inert, and such combination of relays would effect the application of proper current to the lifting magnet of the connector to move the brushes to the next trunk line terminals. When an idle trunk line terminal was reached, both the connecting relay and polariz d relay would operate and said polarized r ay when operating would complete a locking circuit for the said relays from a source of current of proper polarity to maintain itself energized. In case all the trunk lines were busy, when the last one was tested, the current thereat would not maintain the polarized relay energized. an. both the connecting relay and polarized relay would be inert and the usual busy signal applied to the talking circuit.

A further feature of my invention relates to the manner of controlling the diiferent selecting operations of both the primary selector and the connector selected thereby. I provide a bridge of the line conductors leading to the selector, and include in said bridge a polarized relay which in response to currents of different character operates the ditt'crent stepping magnets of the selector. Said selector may employ a stepping magnet o rotate its arm to bring the brushes thereof into operative relation to a row of terminals representing a group of connectors adapted to unite with a given group of telephone lines. Said selector may also be equipped with a lifting magnet adapted to move the contact brushes along the terminals of a selected row to pick out a trunk line lead ng to an idle connector of the group represented by said terminals. Said polarized l lay in the selecting bridge may therefore be double-actmg. and in attractmg its armature in one direction may eii'ect the operation of the rotary magnet of the primary selector. and in rocking its armature in the opposite direction may elfect the operation of said lifting magnet. The said selecting bridge may include another relay which is adapted to control the operation of the stepping magnets of the selected connector. in conjunction with the first-mentioned relay. The connector may be provided with banks of terminals representing groups of. for example, 100 lines each. and the contact carrying arm thereof may be provided with a long step magnet adapted to advance the contact carrying arm in long steps from bank to bank; said arm may be advanced from row to row of terminals of a selected bank by a short step magnet. and along the terminals of a selected row by a lifting magnet. The said first mentioned polarized relay in the selecting bridge at the primary selector may control the operation of the long-step and lifting magnets of the connector. the other relay in the bridge being adapted to operate the short step magnet prior to the operation of the lifting magnet. "the first polarized relay in said bridge. in operating, rende s ineliective the other relay to prevent confusion in the application of selecting currents. The said second polarized relay in the selecting bridge may be a double acting relay, and when its armature is moved in one direction it may operate one of the stepping magnets oi" the connector, and when rocked in the opposite direction when the connector has united with the desired line. it may ctl'ect the operation of the continuity relays of both the distributer and connector to establish the continuity of the testing couductor.

A further feature of my invention coir sists in the provision of means for maintaining the selecting bridge open at all times when it might interfere with the proper operation of the system. Said bridge is maintained open during the process of testing the called line. preferably by the continuity relay of the primary selector. and during the application of ringing current to the called line, the ringing relay may maintain the bridge open. 'hen the called party has responded and the ringing relay has become inert, the continuity relay may again be called into service to maintain said bridge open during the conversation. Said relay is operated, upon the response of the called party, to effect the do energization of the ringing relay. The selector may be provided with rows of terminals, each row representing a group of connectors seriing a given group of telephone lines, and after the selector arm has advanced to the row representing connectors serving the called line. said arm is adapted to hunt automatically along the selected row to locate an idle connector. l provide means for maintaining said bridge at the selector open during the hunt for an idle connector, said bridge when reestablished upon the sclection of such connector. being adapted to complete a circuit tor mechanism of the sending a 'iparatus, which causes said sending apparatus to operate the selected connector. Said selector may haye a lifting magnet adapted to more the arm along a selected row. and a relay may be provided for completing a pulsating current circuit For said magnet. The. said bridgemay be provided with means for cranple ing a momentary circuit for said relay. which causes the magnet to more the arm to the first set of terminals in the row. and if the connector representml by such trunk line is in use. said relay will rec ive current from th} test terminal of the first set. and will maintain the circuit of the lifting magnet. which will advance. the arm to the next set of terminals. and so on until the terminals of an idle con nect r are reached. The connector may be provid d with groups of terminals. and the mechanism at the sending apparatus. operated upon the reestablislunent ot' saidbridge. when an idle connector is located. may con trol the morement of the connector arm from group to group of terminals to the group containing the terminals of the desired line. Finally, it is necessary to maintain said bridge open during the return of the selector arm from operated position to normal position. To this end I employ a relay which is operated during the return of said arm to maintain said bridge open. The circuit of said relay may be established upon the denergization of the retaining magnet of the selector, and may include contacts which are closed while the selector arm is away from normal position, so that when the said arm is completely restored the said relay will be deprived of current.

A further feature of the present invention relates to the provision of improved means for effecting the notification of the operator of the fact that a called party is a member of a party line, whereof the calling party is also a member. To this end I provide a relay having a pair of wind-- ings, one winding whereof is included preferably in the circuits of the relays which control the operative condition of the sending apparatus and the association thereof with the connecting circuit, said winding receiving insullicicnt current to operate the relay armatures until the connector has united with a desired line, whereupon an increased amount of current is supplied to said winding, and it thereupon effects the attraction of said armaturcs. Said'relay in operating connects its other winding in a branch from the connecting circuit. and in case the subscriber with whom c mvcrsation is desired 'is a party on the line which in-- eludes the calling subscriber, said winding will receive sufficient current to maintain the armaturcs of the relay attracted and a peculiar signal will be applied to the con-- necting circuit to indicate to the operator the character of the call.

Another feature of my invention relates to the sending apparatus and consists in the arrangement whereby the particular thousands and hundreds keys representing the digits of a called line cooperate directly with the primary controller in the sending ap paratus, to actuate the primary selector at the selected oilice. and cause the same to unite the operators connecting circuit with a connector adapted to unite with a desired line. Each of the connectors may have its terminals arranged in groups or banks. for example, in banks of one hundred terminals, which may be each subdivided into rows, for example, ten rows, each having ten line terminals. Thus if each connector served five hundred lines. there would be five banks of one hundred terminals.

Another feature of my invention consists in the arrangement whereby an auxiliary controller in the sending apparatus cooperates directly with the depressed hundreds key representing the hundreds digit 01 the called line to move the arm of the selected connector into operative relation to the bank of terminals in which is located the terminals of the called line, and when the auxiliary above outlined, it brings into service again the primary controller, which thereupon cooperates with the depressed tens key repre senting the tens digit of the called line to move the connector arm along the selected bank of terminals into operative relation to the row of terminals in such bank, wherein is located the terminals of the called line. be primary controller, after operating the second time, switches into service again the auxiliary controller, which now operates in conjunction with the depressed units key representing the units digit of the called line to move the connector arm alon the selected row to the line terminals the called party. Thus the primary and auxiliary controllers each operate twice, and each switches the other into service.

Another feature of the present invention is concerned in the arrangement whereby the digit mechanism of the sending apparatus, after being associated with the connecting circuit, is not permitted to operate until the keys representing the digits of the called partys number have been actuated.

I will describe my invention more particularly by reference to the accompanying drawings, which represent a telephone exchange system equipped with an embodiment of my invention, and wherein- Figures 1 to 7 inclusive represent a telephone exchange system embodying my invention; Fig. 8 is a diagrammatic illustration of the grouping of the terminals of the primary selector. Fig. 9 represents a partylin. and its connector terminals; and Fig. 10 represents a private branch exchange having six trunk linesleading to connector terminals; Fig. 11 is a simplified diagram of portions of the primary selector and a connector selected thereby, to illustrate the testing circuit, the manner of establishing thesame, and the mechanism at the selector controlled thereby, for operating the busy signal mechanism: said diagram also showing the method of maintaining the selecting bridge open during the test; Fig. 12 is a simplified diagram of portions of the apparatus and circuits of a distributer or primary selector, to illustrate the means for controlling the application of different sources of ringing current, for selectively signaling stations on party lines. Fig. 13 is a simplified diagram of a portion of the primary selector and a connector selected thereby. sh0.ing the mechanism at the selector controlling the advance of the connector brushes over a row of trunk line terminals to select an idle tru k line leading to a private branch excha. e; Fig. 14 is a simplicontroller has performed the work fied diagram of a. portion of the, primary selector, showing the manner in which the polarized relay in the selecting bridge controls the operation of the stepping magnets of the selector, and also the means employed for maintaining said bridge open during the return of the selector arm from an operated to normal position; and Fig. 15 is a simplified view to illustrate the operation of the reverting call signal controlling mechanism.

Like parts are designated by similar letters of reference throughout the several views.

Referring generally to the system shown as embodying my invention, the operator may be provided with the usual plug for connecting her connecting circuit with the calling line, and said connectin circuit leads to a district selector adapte to pick out the district wherein is located the office where the called line terminates, and to connect sa d connecting circuit with atrunk line leaning to an oflice selector in such district, which picks out a trunk selector adapted to select a trunk line leading to a primary selector at the particular ofiice where the called line terminates. Said primary selector thereupon picks out a trunk line leading to an idle connector adapted to reach the line of the called party. The operation of the said selecting mechanism is controlled by the sending apparatus, which is adapted to be as. ciatcd with the operators connecting circuit after she has answered a call.

The sending apparatus is controlled by oilice thousands, hundreds. tens and units keys. li' the line desired were No. 1465 in the oilice .\'o. the operator would depress key No. 8 of the ofiice keys, key I of the thousands keys. key IV of the hundreds keys, kcy (I of the tens keys and key V of tuc units keys. The ollice key depressed would operate both the district and oilice selectors and conncct the onnau'ting circuit with a trunk liiu leading to a primary selector at ollicc Vl ll, wluu-cupou the thousands an hundreds kcvs depressed vould cause the primary selector to select a connector adapted to reach the called line, and the tens and units keys would operate such connector to finallv unite the connecting circuit with the called linev \Vc will assume that subscriber No. 999, whose line is sir'inn in Fig. l, as terminating in oil No. l. ll'lsll'tih; connection with the line o1 suhrilicr No. lliii'r shown in Fig. 4. \vliosc line terminates at exchange No. 8 in district Xo. f The line of subscriber No. non. Pg. 1 .extends in two limbs from the substation to the central otlice No. 1, where the linc extends through the usual line signal apparatus to the poles of a central battery. At tho central otlice, the usual answering luck 1 is provided. for the line, the thin'ible 16 of said jack being connected with a conductor 17 which leads through the usual cutoff relay to the free pole of a grounded battery 18. The operator is provided with an answering plug 19 with which to unite her connecting circuit with a calling line, the plug 19 and jack 13 constituting a manual connection switch.

The link conductors 20, 21 of the operators connecting circuit lead from the tip and ring respectively of the answering plug, through the windings of the usual repeating coil. between which is bridged the battery 22 in the usual manner. to the line brushes 23, 24: of a district selector Q3, supervisory relays being included in the link conductor 21 on opposite sides of the battery for controlling the usual supervisory signals. The sleeve of the answering plug is connected with a conductor 26 which leads to earth through the winding of a relay 27; said relay 27. whose circuit 26, 17 is completed upon the closure of the connection switch, is provided with an armature 28 controlling the application of current from a battery 29 through the supervisory lamps and contacts of the supervisory relays, which control the display of said lamps, to earth.

Association of stimliny apparatus with cruincctz'ity circm't..\ sending appartus for selectively actuating the line switching mechanism provided for the connecting circuit. is automat cally associated with said connecting circuit when the operator closes her connecting switch to unite the connecting circuit with a calling line, and said sending apparatus is automatically discon nectcd from said connecting circuit when it has completed its work and the switching mechanism has united the connecting circuit with 21 called line.

lho'arinature 3O oi relay 97 in the system shown, controls the association of a sending apparatus with the operators connecting circuit. Said armature is connected with earth, while a front contact thereof is conncctcd with a conductor 31 which leads through contacts of a key 32 to the district selector, thence through the retaining magnet 30 of the district selector, winding 33 of relay 31, contacts the free pole of a grounded battery 35. The retaining magnet 36 is operated by current in this circuit and at its armature 37 and front contact connects the battery with conductor 31 independently of the springs 3 closed only while the selector is in normal condition. Current now flows from the battery 35 through the contacts 3'i' of the retaining magnet, winding of said magnet,

38 of the selector arm. to

conductor 31 to earth. It should be noted [25 that springs 38, when operated at the initial movement of the selector arm, open the portion of conductor '31 including the winding 33 of relay 34. The relay 34 when initially energized, as previously described, attracte its armature 39 and completed a locking circuit for itself independent of the circuit of the retaining magnet, by means of its winding -10. The armature 39 is connected with a conductor 41 which leads in multiple through the winding 40 of the relay 34, and the winding 42 of the switching relay 43 to a wire 44, passing through a winding 45 of relay 46 to the armature 47 of the switching relay 43; said armature 39 when attracted is adapted to engage a contact spring -18 which is con nected by awire 49 with the conductor 31 leading through the armature 30 and front contact of relay 27 to earth. The armature 47 of switching relay 43 controls the connection, of the grounded conductors including the said windings of the relays 34, 43 and 46, with common wires 50, 50', leading respectively to a pair of sending apparatuses F F, said armature 47 its back contact connecting said conductor 44 with common wire 50; and when attracted connecting said conductor 44 with common wire 50.

Assuming that the sending apparatus F is free, and relay 34 has received its initial encrgization as above described, armature 39 of said relay in attracting, causes current to iiow from the tree pole of grounded battery 52 associated with sending apparatus F (Fig. 7) through winding of the controlling relay 53 of said sending apparatus, over the common wire 50 to the connecting circuit. and thence through the armature 47 and back contact of relay 43, conductor 44, winding 45 of relay 46 (without operating the same)thence by way of conductor 41 through the windings 40, 42 of relays 34, 43, respectively in multiple (without operating relay 43) through the armature 39 and contact 48 of relay 34, wire 49 to the conductor 31, which is grounded at the armature 30 and front contact of relay 27. Relay 34 is now locked in circuit with the controlling relay at sending apparatus F. The relay 34 is provided with a grounded armaturev 54 adapted when attracted to engage a front contact connected by a conductor 55 with the tip strand 20 of the connectin circuit, in order to provide a metallic circuit for selecting current as will be later described. The armature 56 of relay 34 is connected with a conductor 57 leading to the armature 58 of switching relay 43, the back contact of said armature being connected with the common wire 59 leading to sending apparatus F. The armature 56 of said relay 34 in its attractive movement is adapted to separate a pair of normally closed springs (10 serially included in the ring strand 21 of the connecting circuit, said armature engaging the member of said springs connected with the portion of the ring strand leading directly to the district selector. The leads to sending apparatus F are now placed while resting against.

1n operative connection with the circuit. The relay 53 at the sending apparatus F in attracting its armature 61 applies current from the free pole of grounded battery 52 to the feed wire 62, a branch from said feed wire leading through a signal lamp to earth in order that the operator may be kept informed as to the condition of the sending apparatus. Said feed wire supplies current for the operation of the mechanism of the sending apparatus. In case the sending apparatus F had been serving another cord circuit, the particular connectin circuit now in use would have been shifted to the sending apparatus F. It will be noted that the feed wire of sending apparatus F has a branch 62 which leads through the winding 63 of the switching relay 43 to a contact spring 64 against which the spring 48 of relay 34 normally rests. Now, if under these conditions the operator had plugged into answer av call, thereby efl'ectin the energization of relay 27, current woul have passed from the branch 62* of the feed wire (which would have been connected with battery 52 of the busy sending apparatus) through contacts 64, 48 of relay 34, to the wire 31 which is grounded at the armature 30 of relay 27, operating relay L3.- The armatures 47, 58 of the switchin relay would thereupon have been attracte and have switched the wires 57, 44, respectively, to the common wires 59', 50', respectively, leading to the sending apparatus F. Furthermore, when the armature 39 of relay 34 had been attracted and the winding 40 of said relay had found a circuit by way of the battery at sending apparatus F, the holding winding 42 of the switching relay would have received current and maintain the switching relay energized.

Operation of ofit'ce keys and district selecto r.In the present system, which is designed for use in a large city, there would be a number of districts in each of which would be located a number of central oflices. I have accordingly employed a district selector arranged to pick out the district in which is located the office desired, and an oflice selector belonging to said district capable of picking out a trunk line leading to the particular otfice desired. I have arranged the office keys so that when a given key is operated it will cause the district selector to locate the proper district, and also actuate an ofiice selector in such selected district to select the proper oflice.

Referring now to the sending apparatus, and to the portion thereof known as the office keyboard, Fig. 5, I will describe the process of picking out a trunk line leading to a primary selector or distributor in ofiice No. 8, in which oflice we have assumed the line of the called party terminates. In this connection, it should be stated that the oflice connecting keyboard is normally in operative relation to the sending apparatus F in order to serve a connecting circuit with which said sending apparatus may be associated; and, when the oilice keyboard has completed its work in conjunction with the sending apparatus F, it autonn'itically transfers itself into operative relation to the sending apparatus I and if the sending apparatus F is taken for use before the lirstmentioned sending apparatus has completed its work. said other keyboard will be locked in its operative relation to the apparatus F. However, assuming that the second sending apparatus is not taken for use, the otlice keyboard will. after the sending apparatus F has completed its work, he re-associatcd with sending apparatus F.

The ollice keys are provided with a pair of controllers (l G, which govern the operation of he district selector and the ollice selector which it selects T he ofiice keys are -ach adapted when depressed to efi'ect the successive operation of the controllers (i a nd l to cause the same to effect the operation of the district selector and pick out a dis trict determined by the particular ollice key depressed; and thereupon the controllers are again successively operated to actuate the selected oflice selector in said district.

Referring first to controller (i. there is provided a row of contacts numbered from 0 to 9, these contacts representing the tens digits of the numbers of the districts. From each one. of said terminals a conductor i3 leads to the springs 66 ot' the particular ollice keys representing ollices lying in the district whose tens digit corresponds to the number of said terminal. In the present case. l have shown springs (34} ol oilice keys Nos. 0. 7 and 9 as connected with the 0 ter minal of the row 0 of contacts.

The controller (i is provided with a rotary arm carrying a brush 71 adapted to sweep over the row (2 of contacts, said arm being provided with a atchet adapted to be operated by stepping and retaining magnets 72. 73. respectively. The brush 71 is connected with a conductor 74 which leads through springs 73 associated with a cut-oil relay 7o. winding of said relay to the Feed wire 77 of the ollirc keyboard. which is nor mally connected through the armature 7S and back contact of a switching relay 79 with the feed wire (3; of the sending appa ratus h.

llach ollice key. when operated. is ar ranged to brine into electrical engagement springs 37. (18. on. which control the starting: of the ollice controller or keyboard a t'ter the sending apparatus with which is asso ciated has becn connected with a particular connecting circuit. The spring (38 is connected with the feed Wire 77 and so with the battery of the sending apparatus. and in engaging spring 69 supplies current to a signal lanip 80, which indicates to the operator the condition of the ofiice keyboard. The spring 07. supplied with current from the feed wire by spring 68, is connected with associated with the cutoff relay 7'3. to a.

,contact of a grounded vibrating arm or pulsator 83. The stepping magnet 72 responds to this current and advances the con tact arm Til. the retaining magnet being sluggish. so that its armature when once attracted. unresponsive to the pulsations. \Vhen the controller arm has taken one step and the brush 71 has engaged the first terminalot' the row 0. the cut-oft relay 76 is operated to open the circuit of the n'iagnets 72, 73, of the controller. current to operate relay 76. passing from the feed wire 77, conductor 74, winding of relay 76. contact springs 77; associated with said relay, brush 71 and terminal 0 to conductor (35. which leads to earth through the contact springs 66. 84. of the ollice key No. which is the key we have assumed to be operated. The relay 76 is provided with a pair of arn'iatures 5 -3, 96. the armature 86, when attracted. separating springs 82 to open the circuit through the magnets oi the controller. said armature engaging the member of said sprin; cv'innected directly with the pulsator 83. The other armature 85 is grounded. and in its attractive movement separates springs 73. engaging the member thereof connected directly'with the winding, of relay 78. there by locking relay 76 to earth from the feed Wire.

The stepping magnet 72. in operating. is adapted to make and break a pair of con tacts 87. which control the application of current from the free ole ol a grounded positive battery 88 to a conductor leading to a common wire 90. which is normally c011- nevrted at the armature 9i and back contact of a switching relay T9 with the common wire 59 ot' the sending apparatus l. in the present case. since this contact arm advanced but one step. but one impulse of current would be supplied by contacts 87 from battery l9 to the common \Vil'cs Qty 39: the common wire .3!) being as before. describ il. connected hy the armature 59 and trout contact of relay 34. Fig. l. with the portion of th ring strand of the connecting circuit leading to the dir-trirt HlOCCOY.

Turning now to the district selector, a number of groups of terminals are. provided. each group representing the terminals of oliice selectors capa le of reaching ofiices in a given number of districts. Thus the selector may have its terminals divided into int m omAwtmnmMmm.

groups of 100 terminals subdivided into ten rows, each row representing a number of selectors representing a particular oflice. and the total number of rows in the group representing the ollice selectors in ten districts. A brush-carrying arm 92, mounted to rotate and to move longitudinally, is provided, having a long step magnet 93 adapted to rotate the arm in long steps, for example, over ten rows of terminals at a step in correspondence with the tens digits of the desired num* bers; the stepping magnet 9t arranged to advance the arm from row to rowof a selected group, while the stepping magnet 95 is adapted to move the arm upwardly to bring the brushes carried thereby into connection with a set of terminals in the selected row connected with an idle ofiice se lector. From the strand 21 of the connecting circuit, the conductor 95 leads through a pair of contacts 96 closed by the arm While in its normal and rotary positions, through the winding of the short step magnet 94, armature 96 and back contact of polarized relay 97, through the contacts 98 of the retaining magnet 36, to earth. A conductor 98 extends in shunt of the stepping magnet 94, said conductor including the long step magnet 93and the armature and back contact of the stepping magnet 94.

The stepping magnets 93, 91 are so arranged that the magnet 93 requires for its operation a smaller amount of current than magnet 9' so that magnet 93 may be operated in the same circuit with the magnet 94, without, however, affecting the latter. When current suitable to operate n'iagnet 9i is impressed upon the circuit, magnet 94 in attracting its armature opens the branch 98 including the stepping magnet 93, so preventing the opcration of said magnet. In the present case, I employ a battery of 24 volts to operate the magnet 93; such current being without effect upon the magnet 94; and in order to operate magnet 94, I use a battery of 48 volts, whereupon magnet 94 operates and opens the branch containing its mate.

When the impulse from the 2% volt battery 88 was applied to common wires 90, 59, and ring strand 21, as previously described, the stepping magnet 93 received sulticieut current for its operation and rotated the arm 92 of the selector through one long step, to the first bank of ten rows of terminals of the district selector, said bank representing the first ten districts.

Returning now to the oliice keyboard, the second controller G' is at this point brought into play to complete the selection ofa district by causing the district selector arm to advance to the row of terminals in' the first bank determined by the units digitof the district in which the particular ,ofiicedesired is located. The controller G is provided with a row a of ten terminals representing the units digits of the districts. From each of said terminals a conductor 98 leads to the springs 9 of the oilice keys representing units digits of oiliccs which lie in the districts whose units digits correspond to the numbers of the terminals in the row 0', that is to say, taking the case of ollice No. 8, the spring 99 of such oflicc key is connected with the terminal 9 of the row 0', which indicates that the units digit of the district in which is located ofiice No. 8 is 9. It should be stated, however, that thisarrangement is purely arbitrary, since spring 99 of oflice key No. 8 could exactly as well have been connected with another terminal of the row 0, depending of course on how the offices are distributed.

The spring 99 of office key No. 8 rests in engagement with spring 84, due to the operation of key 8, and by means of said spring applies a ground to terminal 9 of controller G. The controller G is pro vided with a stepping magnet 102 and a retaining magnet 103. Now, when the cut-off relay 76 was operated to stop the operation of controller G, as before described, it started the operation of the controller G. The armature 86 of relay 76 is connected with a conductor 102, which leads through the contact springs 103 of the cut-off relay 10 1 of controller G, through the stepping magnet 102 of controller G, contacts 105 closed by the controller arm while in normal position, through the retaining magnet 103 to the free pole of a grounded battery 106. Since the front contact of the armature 86 of cut-off relay 76 is connected with conductor 81 and grounded pulsator 83, a circuit 102, 81 will be completed for the magnets 103, 102 of the controller G, and pulsations of current from battery 106 will pass through said circuit, causing the stepping magnet 102 to advance the arm 1.00.

It should be stated at this point that the contacts 105 are for the purpose of prcvent ing access to the controller arm 100 unless the same is in normal position. The contacts are opened as soon as the arm has taken one step, but a branch 107 about said contacts is closed by the armature of the retaining magnet 103, which is sluggish and maintains its armature attracted regariilless of the pulsating character of the current in its circuit, said armature when attracted closing a pair of contacts 109 which control the said branch 107.

The armature of the stepping magnet 10?. in its vibration, makes and breaks a pair of contacts 108", which intermittently applies current from a grounded battery 109 to a conductor 110 which leads to the back contact of the armature 111 of a relay 112, said armature being connected by a conductor 113 with the common wires 90, 59, and so with the ring strand 21 of the connecting circuit. lmpulses from battery 109 therefore pass to the conductor 95 at the district selector. and thence through the stepping ma grnct 91 of the arm 2 to earth. This current of proper strrngl'h to operate magnet 1;. hein r preferably 18 volts. Said magnet f l in operating advances the arm in short step from row to row of the first group of terminals. and in addition, opens the branch 8 containing the long step magnet in order to prevent its operation. This current is of improper polarity to operate polarized relay 9t i the selector.

'lhc lirush 11?] ot' the arm 100 of controller G is connected with a conductor 114 which leads through a winding 115 of a sluggish relay 112, through contact springs 1111 of a cutoff relay 1 H, winding of said relay. to the feed wire 77. Now when the arm 100 has been given a like number of steps, so that its brushes lie below the row ot' terminals representing otliee selectors adapted to reach otlices in district- No. 9, the brush 101 will be in engagement with the grounded. terminal 9 of the row 0', and current will flow from the feed wire 77 through the winding of a cut-oil relay 10.1, winding 115 of sluggish relay 112, brush 191, terminal 9, to earth by way of springs 99, 81 ot otiice key No. 8.

The cut-ottrelay 104 is provided with a pair of armaturcs 117, 118; the armature 111 when :tttt'zlt'tttfl separates the springs 1 to open the circuit of the operating ituzgi'uets oi the controller 1%. while the ar mature 117. which is grounded, in its attractive movement separates springs 116, engaging the member thereof. connected dimay r ith the winding of the cut-otl relay 1M. and so completing a locking circuit for said relay from the feed wire. The separation of said contacts 116 also lareaks the circuit oi" the brush 191, including the winding 11 1 of the sluggish relay 112, which, ho-werer. has had time to attract its armatures.

xiirfommiic mimzimi by district aeiccfor f 17776 (ii/ m sc/(TfioIt Tlie front contact of armature 111 of the sluggish relay 112 is conu cted with a conductor 119 which leads th t ee pole 01' a battery 12(1 of oppd :itc ;'--:;larity to battery 109,-in the present case a grounded negative battery. Current from this battery is 01 proper polarity to operate the. polariyed relay 97 at the district sele tor. w hicl; controls the hunt of the arm 9:; tor an idle otiice selector capable of reaching the oliices in d strict No. 9. (hu rent from said negative battery passes over the ccanuon wires 90, 59, and ring strand :1 to the d strict selector. where said current traverses conductor 95 to one of the members of contacts 913, which is normally connected with a spring 121, and thence over a conductor 122, through the armature 123 and front contact of the retaining magnet 36, winding of relay 97 and contacts 121, closed by the arm 92 while away from normal condition, to earth. The stepping magnets 93, 91, do not respond to this current on account of the rapid attractive movement of the armature 915' of relay 97, which controls the circuit ofrsaid magnets. Relay 97, when thus operated, attracts its armatures 1.25, 126, 90' and.127. The armatures 125, 126, simply maintain the line brushes of the district selector dead during the hunt for an idle otiice selector; the armature 90 in its attractive movement completes a circuit for the lifting magnet 95 and the source of pulsating current 128 by way of conductors 129 and 95, whereupon the arm is lifted to bring its brushes into engagement with the first trunk line termi nals in the selected row. When the arm has taken its first upward step, it separates spring 121 from the contacts 96 and moves said spring into engagement with a contact 139. which connected with a conductor 131, leading to the front contact of the armature 127 of relay 97, which armature in turn is connected by a conductor 132 with the local brush 133 carried by the selector arm. The relay 97 Is now connected directly to earth from the local brush 133 by ay of conductors 132, 131, 122, and in case the said first trunk line is in use, battery will be present at the local terminal 131 thereof, of a proper polarity to maintain relay 97 energized, whereupon the circuit of the stepping magnet 95" will be maintained intact, and the arm 92 lifted another step to bring its brushes into engagement with the teru'iinals of a second trunk line leading to a selector serving oilices in district No. 9. This operation will be continued until the contact brushes of the arm 92 reach the terminals of an idle trunk line, at which time battery will not be present upon the local terminal 131 of such trunk line, and the relay 97 will be de 'n'ived oi current'and will release its aruiatures: arnlature 95' opening the circuit of the lifting? magnet 95, and armature 127 applying at its back contact current from a battery 13;) to conductor 132 and the local brush 1333. in order to lock out other district selectors attempting to make connect on with the trunk line in question.

Operation of ofiz'cc selector under the control of the depre sed 0771706 ]cc7 .-The trunk line selected by the district selector leads in three limbs 136, 137 and 138 to an otlice selector, Fig. 2, adapted to make connection with a trunk line leading to a primary selector at any desired office in district 9, or, as shown, with an idle trunk selector adapted to pick out a trunk leading to the desired ofiice. Said ot'tice selector is provided with rows of terminals representing trunk lines 

